feat(kyberforge): improve skill-author — duality description, source_keys guidance, pre-audit checklists, version bump conventions

- references/sources.md: add YAML frontmatter with source_keys to fix provenance chain break
- SKILL.md description: make create/improve duality explicit ("Handles both the full create flow ... and the improve flow ...")
- SKILL.md Step 2: add inline metadata.source_keys instruction — fill early, not deferred to Step 5
- SKILL.md Step 6 (create) / Step 5 (improve): add pre-audit manual checklists and version bump conventions (minor for create, patch for improve)
- README.md: correct false claim that the skill bumps plugin manifests; it bumps metadata.version only

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0147vXtL5sP6vorDdqXGJJU9

plugins/kyberforge/skills/skill-author/references/sources.md

@@ -1,3 +1,14 @@
+---
+source_keys:
+  - agentskills-home
+  - agentskills-spec
+  - agentskills-best-practices
+  - agentskills-optimizing-descriptions
+  - agentskills-evaluating-skills
+  - agentskills-using-scripts
+  - agentskills-quickstart
+---
+
 # Sources
 
 <!-- agentskills.io/llms.txt was used for initial source discovery and is not listed below; it contributed no skill file content directly. -->